1. Field of the Invention
The present invention relates to an apparatus for and a method of controlling a variable valve timing mechanism that varies valve timing of an engine valve.
2. Description of the Related Art
Japanese Laid-Open (Kokai) Patent Application Publication No. 2005-291200 discloses that when an engine stops, a manipulated variable of a variable valve timing mechanism is feedback-controlled so that valve timing approaches a target of when an engine starts, and the manipulated variable at that time is stored, and then, the stored manipulated variable is output to the variable valve timing mechanism when the engine restarts.
Incidentally, at the start of engine, a start period of time can be reduced by varying valve timing to a target of when the engine starts, without overshooting and with high responsiveness.
However, in the feedback control, since a manipulated variable is set in response to the difference between the target and actual valve timing, when it is intended to avoid overshoot, responsiveness might be deteriorated, and thus a period time before reaching the target might increases.
In contrast, in a feedforward control, although responsiveness can be improved, there is a possibility that overshoot occurs and valve timing is converged to a timing different from the target.